GNU Awk support and documents the "[:blank:]" class:
http://git.savannah.gnu.org/cgit/gawk.git/tree/doc/gawk.1?id=749475a#n1963 GNU Grep supports the "[:blank:]" class as well - but is not documented: http://git.savannah.gnu.org/cgit/grep.git/tree/doc/grep.in.1?id=30e666c#n796
